This is true, if you move all at once.  If you move one space and pause, what happens?  And then continue your move one or two spaces...  not sure myself, will test.

It was like this in FE as well ... I agree it's frustrating.  I was hoping it would have been fixed in LH ... and maybe it will be. 

Seems that if you walk through an area, perhaps you might actually look around you while doing so.    Just sayin'...

^It doesn't even update the terrain. If you have enough movement you can walk far enough where you wont even have the area you traveled through explored, it will just be black. It's crap for exploring AI/neutral roads with high sight units, you have to move one tile at a time or you'll only have these interlocking squares of explored land instead of the strip you'd expect.

While it's true that most of the time you want to move only 1 square at a time, there are times when moving more squares at once would be fine if you weren't losing visibility as a result.  

It's also true that this has always been the case, but that's no reason not to keep bugging them about it.  Squeaky wheel.

I've requested this be fixed in the past, as well.  I've also requested that any fog that's revealed during a turn stay revealed until the turn ends.  Nothing's going to change until you end the turn, so it doesn't make sense to instantly replace fog when you move out of an area.  I don't have a great memory.  I can't memorize everything as I move.